The present invention relates to engine cooling systems.
Generally, a water cooling type engine of a vehicle includes a cooling system provided with a radiator and a flow control valve. The radiator is located in an engine coolant circuit for cooling the coolant. The flow control valve regulates the flow of the coolant that passes through the radiator. The flow control valve is controlled to change the coolant flow in the radiator (hereafter, xe2x80x9cthe radiator flowxe2x80x9d). This adjusts the temperature of the coolant, which cools the engine.
For example, Japanese Laid-Open Patent No. 10-317965 describes a known control procedure of the flow control valve. According to the procedure, the flow control valve is fully closed to minimize the radiator flow when the coolant temperature is relatively low. In contrast, when the coolant temperature is relatively high, the flow control valve is fully opened to maximize the radiator flow. Otherwise, a feedback control procedure is performed to vary the opening size of the flow control valve (the radiator flow) depending on the coolant temperature, such that the coolant temperature seeks a predetermined target.
In other words, the control state of the flow control valve is changed, as needed, among a fully closed state, a fully open state, and a feedback control state. This controls the coolant temperature appropriately.
When the control state of the flow control valve is being changed from one state to another, the flow control valve is being subjected to transitional controlling. If the transitional controlling is inappropriate, a certain problem may occur. It is thus important to optimize the transitional controlling to ensure that the transitional controlling is conducted appropriately. However, switching of the control states of the flow control valve involves various different modes and purposes. This makes it difficult to perform the transitional controlling always reliably for meeting the requirements of a certain mode or achieving a certain purpose.
Accordingly, it is an objective of the present invention to provide an engine cooling system that appropriately performs transitional controlling of a flow control valve when changing the control mode of the flow control mode from one mode to another.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, the invention provides an engine cooling system that includes a coolant circuit, which extends through an engine, a radiator, which is located in the coolant circuit and cools the coolant that flows in the coolant circuit, a flow control valve, which regulates the amount of the coolant that passes through the radiator, and a controller, which controls the flow control valve for adjusting the temperature of the coolant that flows in the engine. The controller controls the flow control valve in accordance with a control mode selected from different types of control modes. The controller performs a transitional control procedure selected from different types of transitional control procedures when switching from one control mode to another.
The present invention also provides a method for controlling an engine cooling system. The system includes a coolant circuit that extends through an engine. The method includes: cooling coolant that flows in the coolant circuit with a radiator located in the coolant circuit; regulating the amount of the coolant that passes through the radiator with a flow control valve; controlling the flow control valve in accordance with a control mode selected from different types of control modes; and controlling the flow control valve in accordance with a transitional control procedure selected from different types of transitional control procedures, when switching from one control mode to another.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.